Asphalt is a mixture of various size aggregates and asphalt bitumen to make asphaltic concrete. The aggregates are segregated and blended by size in an aggregate blending system and appear as a single flow of material entering the drum mixer. There are State requirements that this blend of aggregate be checked by sampling at various intervals. The most commonly used sampler is a trolley type device which mounts on the head end of the conveyor that is provided to move the blended aggregate to the drum mixer.
The aggregate, composed of a variety of sizes, does not load the conveyor evenly and there is a tendency toward some segregation based upon the size, shape and density properties of each piece. Generally the larger aggregates migrate to the periphery while the smaller sizes are concentrated in the middle of the material stream. Thus, it has been found that the trolley type sampler does not capture a full cross-section of the material discharged from the conveyor due to the discharge characteristics of the material discharging from the moving conveyor. As is known, the discharge characteristics of aggregate from a moving conveyor is in the propensity of the aggregate as it leaves the confines of the conveyor belt to fan radially outwardly. Thus, the larger size aggregate which naturally graviate to the sides of the belt are missed by the known trolley samplers. This coupled with the segregation of the different sizes of the material indicates that a basic sample is not collected.